Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mitochondrial dihydroorotate dehydrogenase (DHODase), the single redox reaction in the pyrimidine de novo synthetic pathway, was purified to near homogeneity by detergent solubilization and fast protein liquid chromatography (FPLC) techniques from the mature trophozoites and schizonts of Plasmodium falciparum, human malaria parasite. The purified DHODase was monofunctional protein with a M(r) of 56,000 +/- 4000, based on Superose 12 gel filtration FPLC and SDS-PAGE analyses. Polyclonal antibodies raised against the purified P. falciparum protein was cross-reacted with P. berghei, rodent malaria parasite. The optimal activity of DHODase required long chain of coenzyme Q (CoQ6-10) which were essential for electron transfer. The Km and kcat values for L-dihydroorotate were 14.4 +/- 5.9 microM and 15.0 +/- 1.4 min-1, respectively; for CoQ6, they were 22.5 +/- 6.4 microM and 21.6 +/- 3.4 min-1. L-Orotate, an enzymatic product, was a strong competitive inhibitor with Ki of 18.2 +/- 3.6 microM. The 5-substituted L-orotates having antimalarial activities against P. falciparum in vitro were found to be competitive inhibitors. The inhibitory effect by these 5-substituted L-orotates on the malarial DHODase was different from the mammalian enzyme. Various benzoquinones and naphthoquinones were found to inhibit the purified DHODase activity at a different degree. Mitochondria from erythrocytic cycle of P. falciparum were purified, using differential centrifugation and followed by Percoll density gradient separation, with purifications of 13-fold and overall yields of 33%. The double-membraned mitochondria had a few tubular-like cristae structure as what found in many protozoan parasites. DHODase was localized inside the mitochondria as probed by immunogold labeling with the polyclonal antibodies and selective solubilization by digitonin.
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PMID:Purification, characterization and localization of mitochondrial dihydroorotate dehydrogenase in Plasmodium falciparum, human malaria parasite. 772 9

The effects of peptide proteinase inhibitors on globin hydrolysis by cultured malaria parasites were studied. All of the four cysteine proteinase inhibitors evaluated blocked globin hydrolysis, as documented by the development of a morphological abnormality in which parasite food vacuoles filled with undegraded globin and by SDS-PAGE showing that the cysteine proteinase inhibitor-treated parasites accumulated large quantities of globin. The aspartic proteinase inhibitor pepstatin did not block globin hydrolysis by cultured parasites. None of seven antimalarial drugs tested elicited the food vacuole abnormality caused by cysteine proteinase inhibitors, indicating that this morphological alteration was not simply a sign of nonspecific parasite toxicity. Our results indicate that a trophozoite cysteine proteinase is required for initial cleavages of globin by intact malaria parasites.
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PMID:Plasmodium falciparum: effects of proteinase inhibitors on globin hydrolysis by cultured malaria parasites. 789 37

The specificity of lymphocyte proliferative responses of malaria patients and healthy control subjects was analysed using antigen fractions from soluble extracts of purified Plasmodium falciparum schizonts. Fractions of 14-250 kDa were separated by SDS-PAGE, blotted to nitrocellulose membranes and eluted for use in lymphocyte stimulation studies. Lymphocyte proliferation following stimulation with the separated protein fractions demonstrated that the fractions were recognized only by patients' T cells. Moreover, only the fractions including proteins of 36-250 kDa were immunogenic to the T cells. The pattern of response against each fraction differed between patients, indicating an HLA-dependent genetic restriction in the T cell activation.
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PMID:Proliferative responses of lymphocytes from malaria patients and healthy controls to isolated, Plasmodium falciparum schizont antigens. 819 11

Duffy blood group antigenic epitopes are located on a 35-43 kD integral membrane protein of the erythrocyte membrane. This protein functions as a receptor for the human malaria parasite, Plasmodium vivax. The Duffy protein has been difficult to purify because of its tendency to form aggregates. Here we describe purification of a 28 kD tryptic fragment of the Duffy protein and purification of an 18 kD de-glycosylated form of the Duffy tryptic peptide using Thiopropyl Sepharose 6B chromatography and preparative SDS-PAGE. These Duffy-reactive peptides do not form aggregates and may prove amendable to protein sequencing.
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PMID:Purification of a 28 kD non-aggregating tryptic peptide of the Duffy blood group protein. 848 49

Previous studies have indicated the inositol monophosphate (IMP) is a component of the malaria parasite toxin that induces cytokines such as tumour necrosis factor (TNF). To further characterize the toxin we have labeled Plasmodium falciparum in vitro cultures with [14C]inositol or [35S]-methionine and immunoprecipitated the labeled antigens with an antiserum against IMP which blocks malaria parasite-induced TNF production. We detected four proteins associated with IMP when the immunoprecipitates were separated by SDS-PAGE and analyzed by autoradiography. To evaluate the capacity of different P. falciparum antigens to induce cytokine production we separated a mixture of exoantigens by SDS-PAGE gels. Antigen fractions of 43-71 kDa and of a low molecular mass of <20 kDa contained the dominant inducers of TNF alpha interleukin 1 alpha, and interleukin 6 production from human mononuclear cells. The low-molecular-mass antigen fraction contained hemoglobin, while no parasite-specific proteins were detectable when tested by immunoblotting. Hemoglobin may act as a carrier for cytokine-inducing malaria parasite toxins.
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PMID:Plasmodium falciparum: characterization of toxin-associated proteins and identification of a hemoglobin containing parasite cytokine stimulator. 861 41

The major form of glutathione S-transferase (GST) activity from the mosquito Anopheles dirus (species B), a vector of malaria in Thailand has been purified 421-fold. It constituted approx. 20% of the total measured CDNB conjugating activity in the homogenate. This enzyme appeared as a single band of 25.0 +/- 0.26 kDa on SDS-PAGE and was kinetically characterized with 10 substrates and 4 inhibitors. The enzyme is capable of catalysing dehydrochlorination of 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane (DDT) in vitro at a rate of 4.4 nmol of 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane (DDE) formation per mg protein. This is comparable to the rate of catalysis of the orthologous isoenzyme from An. gambiae reported previously. The IC50 plots of the inhibitor data (fractional velocity vs log [I]) for three of the inhibitors indicate the homogenous nature of this enzyme. However, inhibition by ethacrynic acid demonstrates more than a single affinity site for interaction. The six N-terminal amino acids of the purified enzyme are identical to a GST reported from Aedes aegypti, which was indicated to play a role in DDT-resistance in this species. The results suggest that the two enzymes may belong to the same class, however each possesses a different specificity.
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PMID:Purification and characterization of a major glutathione S-transferase from the mosquito Anopheles dirus (species B). 890 May 97

Sporozoite recognition of host cells is a key step in the life-cycle of malaria parasites. Two sporozoite proteins have so far been characterized in some detail, the circumsporozoite protein (CS) and thrombospondin related adhesive protein (TRAP). We report here the cloning and expression of the TRAP gene homologue from Plasmodium berghei, PbTRAP. The PbTRAP gene encodes a protein of 606 amino acids having a deduced molecular mass of 66 kDa. The overall structure is clearly that of the TRAP family having a signal sequence followed by an integrin A domain, a sulphatide binding motif, followed by a proline based repeat before a transmembrane domain and helical cytoplasmic tail. The observed molecular mass is almost 50% larger than expected, this can be explained almost entirely by the abnormal behaviour in SDS-PAGE of the proline based repeat. As would be expected PbTRAP shows greatest similarity with the P. yoelli TRAP homologue sporozoite surface protein 2 (SSP2) than with PfTRAP, the TRAP gene from P. falciparum. The pattern of expression is similar to that of SSP2.
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PMID:Cloning and expression of the thrombospondin related adhesive protein gene of Plasmodium berghei. 904 16

Malaria parasites break down human hemoglobin to its constituent amino acids by cysteine and aspartic proteinases. However, no one has previously been able to identify hemoglobin cleavage products in intact parasites. When isolated parasites were subjected to non-denaturing polyacrylamide gels electrophoresis, a unique protein band was found which contains heme and reacts with anti-human hemoglobin antibodies. This protein does not appear to represent oxidized or glycosylated hemoglobin, and is present in isolated parasites but not in the cytosol of infected or uninfected erythrocytes. When this band was eluted and subjected to SDS polyacrylamide gel electrophoresis, three bands were seen on Western blots. The proteins in these bands contain proteins with the N-terminal sequences of alpha- and beta-globin chains but molecular masses of only 13.2-13.4 kDa. These data suggest that hemoglobin alpha- and beta-chains are initially cleaved within the parasite phagolysosome to release peptides of 15-17 and 23-25 amino acids from the C-termini of alpha- and beta-globin chains, respectively. Production of the hemoglobin breakdown products was inhibited by E-64, a cysteine proteinase inhibitor, suggesting the involvement of a cysteine proteinase in an early step of hemoglobin degradation.
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PMID:Identification of hemoglobin degradation products in Plasmodium falciparum. 920 Jan 24

The malaria parasite Plasmodium falciparum synthesizes a protein, Pf155/RESA, which associates with the membrane of newly invaded erythrocytes. Using spent supernatants from P. falciparum growing in culture as a source of soluble Pf155/RESA, we have developed a purification technique based on the concentration of these supernatants, followed by gel filtration and continuous elution electrophoresis. SDS-PAGE electrophoresis and immunoblots were used to establish the quality of the purification.
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PMID:Purification of Pf155/RESA antigen from supernatants of in vitro Plasmodium falciparum cultures by continuous elution electrophoresis. 943 57

Japanese isolates of Bacillus thuringiensis were screened for larvicidal activity against the mosquito Anopheles stephensi, the urban malaria vector of the Indian subcontinent. Among more than 30 strains identified, larvicidal activity causing > 80% mortality in 72 h was demonstrated for 41/1449 (2.8%) isolates. The majority of strains and isolates (97.2%) exhibited little or no larvicidal activity. Anopheles-active strains belonged to more than 12 H serotypes, especially H3ade (serovar fukuokaensis) and H44 (serovar higo). SDS-PAGE profiles of inclusion proteins showed 4 distinct types among 6 active strains examined. The most active Japanese isolates were H20 strain 89-T-34-14 (LC50 4.4 micrograms/ml) and H44 serovar higo strain 74-E-45-24 (LC50 7.6 micrograms/ml), respectively, 13-fold and 23-fold less active than the international standard H14 serovar israelensis (LC50 0.33 microgram/ml).
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PMID:Larvicidal toxicity of Japanese Bacillus thuringiensis against the mosquito Anopheles stephensi. 951 45


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